The present invention relates to an exhaust structure for an internal combustion engine.
Japanese Laid-Open Patent Publication No. 2013-24205 discloses an exhaust structure for an internal combustion engine. The exhaust structure includes a turbine housing of a turbocharger located in the middle of an exhaust passage. The turbine housing defines an accommodation space accommodating the turbine wheel and includes a scroll passage through which exhaust gas is drawn into the accommodation space. The turbine housing also includes a discharge passage through which exhaust gas is discharged from the accommodation space. The discharge passage is connected to the accommodation space. In addition, the turbine housing includes a bypass passage. The bypass passage bypasses the accommodation space to connect the scroll passage and the discharge passage.
An air-fuel ratio sensor that detects an air-fuel ratio (partial pressure of oxygen) in the exhaust passage is attached to the turbine housing. The air-fuel ratio sensor includes a distal end that projects into the discharge passage to detect an air-fuel ratio. The distal end of the air-fuel ratio sensor is located closer to the center axis of the bypass passage than the center axis of the accommodation space.
In the exhaust structure, the distal end of the air-fuel ratio sensor is located in the proximity of the bypass passage. Thus, exhaust gas discharged from the bypass passage greatly affects the air-fuel ratio detected by the air-fuel ratio sensor. However, in order to accurately detect the air-fuel ratio of exhaust gas in the entire exhaust passage, both the air-fuel ratio of exhaust gas discharged from the bypass passage and the air-fuel ratio of exhaust gas discharged from the accommodation space of the turbine wheel need to be reflected on the air-fuel ratio detected by the air-fuel ratio sensor.